332  
FXUS02 KWBC 021556  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1156 AM EDT FRI NOV 02 2018  
 
VALID 12Z MON NOV 05 2018 - 12Z FRI NOV 09 2018  
   
..OVERVIEW
 
 
BROAD CYCLONIC FLOW WILL DOMINATE THE LOWER 48 NEXT WEEK IN A  
PATTERN THAT WILL FEATURE BELOW AVERAGE TEMPERATURES FOR THE  
CENTRAL US BEHIND A DEEPENING AREA OF LOW PRESSURE LIFTING THROUGH  
THE GREAT LAKES ON TUESDAY. A STALLED FRONT ALONG THE EAST COAST  
WILL KEEP A CHANCE OF RAIN FOR MANY COASTAL AREAS EARLY IN THE  
WEEK PRECEDING THE GREAT LAKES SYSTEM. WEAKER SYSTEMS EMBEDDED IN  
THE NORTHWEST FLOW ALOFT WILL DIVE OUT OF SOUTHWESTERN CANADA INTO  
THE TROUGH WHICH MAY SPREAD LIGHTER RAIN/SNOW FROM THE NORTHWEST  
THROUGH THE ROCKIES.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE MODELS AND ENSEMBLES REMAIN MOSTLY WELL-CLUSTERED THROUGH THE  
PERIOD WITH GENERALLY TIMING DIFFERENCES AMONG THE GUIDANCE. A  
CONSENSUS APPROACH HAS BEEN THE MOST STABLE GUIDE AND THE 06Z GFS  
AND 00Z ECMWF FALL NEAR THAT OVERLAP THROUGH MOST OF THE PERIOD  
WITH THE 00Z CANADIAN MOSTLY IN LINE AS WELL. THIS MAINTAINS THE  
CENTRAL US TROUGH THROUGH THE END OF NEXT WEEK AS THE DOWNSTREAM  
ATLANTIC RIDGING MEANDERS IN PLACE AND THE UPSTREAM PACIFIC RIDGE  
SHIFTS BETWEEN 130-160W AS SYSTEMS SLIDE UP AND OVER IT NEAR  
ALASKA.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
TEMPERATURES WILL BE BELOW AVERAGE FROM THE NORTHERN ROCKIES  
THROUGH THE PLAINS INTO THE GREAT LAKES AND OHIO VALLEY AS  
REINFORCING COLD FRONTS DRAG COOL/COLD CANADIAN AIR THROUGH THE  
REGION. THE WEST WILL SEE NEAR TO ABOVE AVERAGE TEMPERATURES  
THANKS TO UPPER RIDGING WHILE THE EAST WILL BE A BIT VARIABLE --  
WARMING UP AHEAD OF THE GREAT LAKES SYSTEM TUE/WED THEN COOLING  
OFF AFTER THE FRONT PASSES. SOME RECORDS HIGHS MAY BE POSSIBLE  
AHEAD OF THE FRONT ACROSS THE SOUTHEAST/FLORIDA TUE/WED.  
 
PRECIPITATION WILL BE CONCENTRATED AROUND TWO SYSTEMS: 1) ALONG A  
STALLED FRONT NEAR THE EAST COAST MON-TUE AND 2) WITH THE  
MID-MISSISSIPPI VALLEY/GREAT LAKES SYSTEM TUE/WED. THE FORMER HAS  
SHOWN THE POTENTIAL FOR HEAVY RAIN ALONG THE COAST FROM SC TO THE  
MID-ATLANTIC BUT THIS MAY REMAIN JUST OFFSHORE. THE LATTER SYSTEM  
HAS MUCH STRONGER FORCING BEHIND IT FROM ALOFT AND AT THE SURFACE  
AND WILL BRING INCREASINGLY WINDY AND WET CONDITIONS TO THE MIDDLE  
MISSISSIPPI VALLEY NORTHWARD INTO THE GREAT LAKES AS THE SURFACE  
LOW WINDS UP RATHER QUICKLY. SEVERE WEATHER WILL ALSO BE POSSIBLE  
IN THE WARM SECTOR IN THE SOUTHEAST AND THE STORM PREDICTION  
CENTER HAS OUTLINED MON/TUE AS THE BEST CHANCE OF ORGANIZED SEVERE  
WEATHER. AFTER THE SYSTEM LIFTS INTO CANADA, COLDER AIR WILL WORK  
INTO THE GREAT LAKES IN ITS WAKE WITH 850MB TEMPERATURES DROPPING  
TO -12 TO -15C OVER LAKE TEMPERATURES AROUND +5 TO +10C (AND  
SURFACE TEMPERATURES IN THE UPPER 20S AND LOW 30S F. THIS COULD  
SUPPORT A SIGNIFICANT LAKE EFFECT SNOW EVENT FOR THE UP OF  
MICHIGAN AND NORTHERN LOWER MICHIGAN LATE NEXT WEEK THOUGH THE  
FLOW MAY BE VARIABLE AS WEAKER SYSTEMS ROTATE THROUGH. TO THE  
SOUTH, THE FRONT MAY SINK WELL INTO THE GULF WITH COOLER/DRIER AIR  
PUSHING THROUGH MOST OF FLORIDA EXCEPT FOR PERHAPS MIAMI AND THE  
KEYS. ADDITIONAL RAIN MAY EXPAND THROUGH THE LOWER MISSISSIPPI  
VALLEY LATER NEXT WEEK WELL NORTH OF THE FRONT IN A WEAK  
OVERRUNNING ENVIRONMENT WITH THE FLOW ABOVE THE SURFACE OUT OF THE  
WESTERN GULF.  
 
FRACASSO  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES ARE FOUND AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 
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